A flipper has an expanded blade that enables an increased propelling force when a diver kicks water, and therefore helps the diver to move quickly under water.
The blade of the flipper preferably has a proper rigidity matching the diver's kicking force, so as to produce a propelling force to move the diver forward. The blade is also provided at two outer sides with elastic and tough side rails to enhance the side strength of the blade and provide the blade with a restoring force for the blade to restore from a bent and deformed state during kicking water.
The currently available flippers normally include a plurality of rigid skeleton plates obliquely arranged on the blades, and a flexible web structure associated with the skeleton plates in the process of molding.
The flexible web structure is made of rubber and integrally formed at each outer side with a side rail having a particularly enlarged cross section to give the blade fixed outer edges and sufficient elasticity to restore the blade from a bent and deformed state during kicking water.
Since the side rails on the blade of the conventional flipper are made of a soft material and do not internally include any tough supporting structure, they must be particularly thick to effectively support the weight of the blade and possess sufficient elasticity and toughness for the blade to restore from the deformed state. The thick side rails would inevitably increase the volume at two lateral sides of the blade and the overall weight of the flipper, forming an increased load to the diver to consume more strength during kicking water. Moreover, the rigid skeleton plates of the conventional flippers are obliquely arranged on the blade instead of being lengthwise extended on the blade. The obliquely arranged skeleton plates prevent the blade from deforming in a transverse direction like a bowl, and accordingly, lead to reduced kicking force and propelling force.